People routinely use the Internet to review services from plumbers to hairdressers. Now the tables are turned. Companies are rating their customers, shunning those who do not make the grade.

Hussein Kanji insists he is not a bad Uber passenger.

“I’ve asked drivers to turn up or down heat, to not play music loudly, or to roll up windows,” Mr. Kanji, a London venture capitalist, said. “I can’t imagine why they would lower my passenger score.”

They apparently did. The wait for a ride suddenly became interminable. “For about three weeks, Uber was basically unusable,” Mr. Kanji said.

Customer reviews are a new form of credit report, one that measures comportment instead of finances. Although such ratings have been tried before — eBay was a pioneer — the practice has taken off with the rise of the so-called on-demand economy.

Strangers may be eager to drive you places or rent you their house for the weekend, but they require some level of confidence. So companies from Airbnb to the new taxi services use reviews to weed out those they do not wish to serve.

In response, some consumers are becoming more polite and prompt. But the knowledge that they may be rated is also encouraging people to submit more upbeat reviews themselves, even if the experience was less than stellar. When services choose whom to serve, no one wants to be labeled difficult.

“It’s a Barney world,” said Michael Fertik, the chief executive of Reputation.com, referring to the purple dinosaur who sings, “With a great big hug and a kiss from me to you/ Won’t you say you love me too.”

Reviewing customers is also raising questions about who owns the data detailing good and bad behavior, what they can do with it — and whether people even know it is being collected.

“You take a college class and even though you’re paying, you’re going to get a grade,” said Catherine Sandoval, a member of the California Public Utilities Commission, which regulates cab services. “You know that’s what you signed up for. Now you’ve being graded as a passenger, as a guest, as a customer. The information is stored and shared. There’s little transparency.”

Ms. Sandoval sees a cab ride as a chance to make a phone call or send a message or read a report. But if she is taking Uber, she makes sure her silence won’t be misinterpreted.

“I say, ‘I’m sorry, I have some work to do. Please excuse me,’ ” she said. “If the driver is a tour guide or a philosopher, you don’t want to alienate them.”

EBay pulled back on allowing sellers to review customers in 2008. Buying on eBay is a straightforward transaction with little personal interaction between seller and buyer, and so the reviews got in the way. Now eBay allows sellers to make only positive comments about buyers.

But the new platforms let reviews go both ways, and vary in their transparency about the process. Yelp is straightforward: Businesses can post replies to critical customers. On Lyft, the second-biggest of the new cab companies, passengers are vaguely warned that “a low star rating” means requests for rides may not be accepted. Uber does not mention passenger ratings at all in its user agreement but noted in a blog post that “an Uber trip should be a good experience for drivers too.”

It does not seem to take much to annoy some Uber drivers. On one online forum, an anonymous driver said he gave poor reviews to “people who are generally negative and would tend to bring down my mood (or anyone around them).” Another was cavalier about the process: “1 star for passengers does not do them any harm. Sensible drivers won’t pick them up, but so what?”

Even those who know Uber best appear surprised by how easy it is to fall from grace. “I was at a 5 for a long time, then I had a string of 4 stars,” Travis Kalanick, the company’s chief executive, recently told San Francisco magazine. “I don’t know what happened. I think what happened was I was a little stressed at work. I was not as courteous as I should have been.”

Part of the confusion stems from the fact that the rental economy — taking its cue from the Internet in general — sees everything as either horrible or great, with little room for nuance. Lyft nods to this when it tells passengers reviewing drivers that “anything lower than 5 indicates that you were somehow unhappy with the ride.” Drivers can be dropped from their services when they fall below 4.5, but it is unclear what it takes to get banned as a passenger.

“Have riders been given a temporary cooling-off period or barred from using the app for inappropriate or unsafe behavior? Yes,” Uber said in a blog post, adding that it wanted only “the most respectful riders.” It declined to be more explicit.

Even as the rules are being worked out, those who monitor the reputation economy most closely believe that the services will begin to meld their reviews.

“Highly specific pools of reputation information will become more useful in aggregate,” said Mr. Fertik, co-author with David C. Thompson of “The Reputation Economy,” a guide to optimizing digital footprints. “If you’re a really good Uber passenger, that may be useful information for Amtrak or American Airlines. But if you add in your reputation from Airbnb plus OpenTable plus eBay, it starts to get useful globally.”

He added: “It’s inevitable that these review systems are coming. What I’m worried about is whether they’re accurate enough. Otherwise, we’re going to get a disinformation economy.” Will a review system know that someone gets out to the cab a little late because of mobility issues, instead of discourtesy?

Researchers are beginning to examine bilateral review systems, where the services and consumers give their opinions of each other, and seeing problems that did not exist when criticism flowed only one way.

Georgios Zervas, Davide Proserpio and John W. Byers of Boston University released on Friday their academic paper, “A First Look at Online Reputation on Airbnb, Where Every Stay Is Above Average.” They looked at more than 2,000 properties listed on both Airbnb, which allows hosts to rate guests, and TripAdvisor, which does not.

In theory, the reviewers should say the same thing on each service. But on Airbnb the enthusiasm is much more palpable. The number of cross-listed properties rated 4.5 stars or above is 14 percent higher on Airbnb than on TripAdvisor. The number that receive 5 stars, a perfect score, is 18 percent higher.

The Hotel Tropica in the trendy Mission District of San Francisco is a case study in contrasting reviews. On TripAdvisor, the opinions of the budget accommodations are negative. “Bug bites!” one guest complains. “Extremely expensive for the low quality,” another says. Eighteen out of 39 reviewers rank the hotel “terrible.”

On Airbnb, 45 reviewers give threedifferentrooms at the Tropica an average of four stars. The guests strive in their comments to look on the bright side. “Beds were comfortable and relatively clean (some hairs on pillows etc),” wrote one. Said another:“Rooms are very very noisy but comfortable.” A third: “It was very hot at night so we left our windows open so we heard a lot of noise, but it was manageable!”

The privately owned Tropica did not respond to email or phone messages. Airbnb said it tweaked its review system last summer to encourage more frequent and more honest reviews of hosts. But the Boston University researchers conclude that letting hosts openly review the guests may make the guests more generous, or at least more wary.

“There are incentives that encourage the overreporting of positive experiences and the underreporting of negative experiences,” Mr. Zervas said.

One theory: If Airbnb guests seem too critical they might get turned down by future hosts who worry they will be too demanding. Who wants a cranky guest complaining about the noise at 3 a.m.? A better approach is just to shower everyone and everything with praise.

“You’re going to have a great time,” Mr. Zervas said. “Whether you like it or not.”

A version of this article appears in print on , on Page A1 of the New York edition with the headline: Ratings Now Cut Both Ways, So Don’t Sass Your Uber Driver. Order Reprints | Today’s Paper | Subscribe